Loading collection data...
Collections are a way for you to organize kata so that you can create your own training routines. Every collection you create is public and automatically sharable with other warriors. After you have added a few kata to a collection you and others can train on the kata contained within the collection.
Get started now by creating a new collection.
lines like
.toLowerCase() // transform the word to lowercase to ignore case
might look good when you are learning, but a code should be readable by itself, the function toLowerCase is pretty descriptive by itself, so it shouldn't need comments.
I like that you didn't use .map(Number) in the version splits, because then you'd have two more unecessary loops.
I forked it for this exact same reason, could you comment on it?
I think this is the best one I've seen, I'd use Template literals in the return statement tho.